HorseCalcs: Bootstrapped Figures for the Working Rider
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Horse hay calculator

Horses eat about 2% of their body weight in forage a day, and some of what you put out gets wasted. Enter your horses and your bales to see how many you need for the season, what it will cost, and whether the hay in your barn will last.

Enter your numbers
Horses
1.5–2.5%. Use 2% for most horses on hay alone.
Hay and season
Weigh a few; small squares run 40–70 lb

Bales needed

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Eaten per horse
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Put out per day (with waste)
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Total hay
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Cost
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Hay on hand lasts
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Buy extra

Bale weights vary more than you'd expect, and a hard winter adds feeding days. Most horse owners buy 10–20% more than the math says, or line up a second source before they run short.

How much hay a horse eats

Hay per day = body weight × 1.5–2.5%
Hay to buy = daily hay × horses × days ÷ (1 − waste)

The National Research Council recommends horses eat at least 1.5% of body weight in forage dry matter a day, and most do best around 2% when hay is their main feed. An 1,100 lb horse on hay alone eats about 22 lb a day. Easy keepers may need less; hard keepers, growing horses and horses in cold weather need more.

Waste matters

Hay fed on the ground can lose 15–25% to trampling and soiling. Round bales without a feeder can lose up to 40%. Hay racks, slow-feed nets and round-bale feeders cut waste to 5–12%, and often pay for themselves in one winter.

Don't know your horse's weight? Start with the horse weight calculator. To check whether hay alone meets energy and protein needs, use the horse feed calculator.

Frequently asked questions

Why does the calculator ask how I feed hay, not just how much?

Feeding method changes how much of the hay actually gets eaten versus wasted — hay on bare ground can lose 15–25% to trampling and soiling, while a hay rack or slow feeder cuts that down to 5–10%, which meaningfully changes how much you actually need to buy.

What if I don't know my horse's weight?

Use the horse weight calculator first — it estimates weight from two tape measurements — since an accurate weight is the starting point for the whole hay calculation and a rough guess can throw off the total by a meaningful margin.

Is 2% of body weight right for every horse?

It's a solid default for most horses on hay alone, but easy keepers may do fine on less and hard keepers, growing horses, or horses in cold weather often need more — the calculator's 1.5–2.5% range exists because the right number genuinely varies by individual horse.

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